JP3342341B2 - Liquid crystal device and driving method of liquid crystal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device having a liquid crystal element, and more particularly to temperature compensation of a liquid crystal element using a memory liquid crystal.

[0002]

2. Description of the Related Art In recent years, a liquid crystal device using a memory liquid crystal such as a ferroelectric liquid crystal (FLC), an antiferroelectric liquid crystal (AFLC), and a bistable twisted nematic liquid crystal (BTN) has attracted attention. The liquid crystal device has an advantage that large-capacity display is possible due to its memory property, but has a disadvantage that element characteristics easily change with temperature change.

Therefore, a proposal for compensating for this disadvantage by a driving method is disclosed in, for example, FLC in Japanese Patent Application Laid-Open No. 60-123.
No. 825, JP-A-62-118326, and JP-A-63-44636.
No. 75041.

[0004]

However, in the conventional liquid crystal device employing these driving methods, the temperature compensation over the entire operating temperature range of the liquid crystal element cannot be sufficiently performed, and the temperature compensating method becomes complicated. There is a problem that the cost of the control circuit and the like increases.

Accordingly, the present invention has been made to solve such a problem, and provides a liquid crystal device and a driving method of the liquid crystal device which can perform sufficient temperature compensation of a liquid crystal element with a simple structure. It is intended to do so.

[0006]

According to the present invention, there is provided a liquid crystal element adapted to drive a liquid crystal sandwiched between a pair of substrates by applying a drive signal to electrodes formed on the pair of substrates. A driving voltage generating means for generating a driving voltage for driving the liquid crystal, a driving signal generating means for generating a driving signal having a magnitude corresponding to the driving voltage, and a temperature for detecting a temperature of the liquid crystal element. Detecting means, based on the temperature information from the temperature detecting means, determines which temperature area of the plurality of temperature areas the temperature of the liquid crystal element belongs to has a predetermined temperature range, The driving voltage generating means is controlled so that the driving voltage becomes a predetermined constant voltage different from other temperature regions, and the pulse width of the driving signal is changed in the temperature region according to the temperature. It is characterized in that and a control means for controlling the drive signal generating means.

Further, the present invention is characterized in that the control means controls the drive voltage generation means such that the drive voltage in the temperature region on the low temperature side is higher than the drive voltage in the temperature region on the high temperature side. Things.

Further, the invention is characterized in that the control means shortens a pulse width of the drive signal in response to a temperature rise.

Further, the present invention is characterized in that the liquid crystal is a liquid crystal having a memory property.

Further, the present invention is characterized in that the liquid crystal is a ferroelectric liquid crystal or an antiferroelectric liquid crystal.

Further, the present invention is characterized in that the liquid crystal is a bistable nematic liquid crystal.

According to the present invention, there is provided a liquid crystal device having a liquid crystal element having a configuration in which a driving signal is applied to electrodes formed on at least one substrate to drive a liquid crystal interposed between the pair of substrates. In the driving method, when the temperature of the liquid crystal element is within a first temperature range having a predetermined temperature range, the driving voltage is constant based on temperature information from a temperature detecting unit that detects the temperature of the liquid crystal element. While changing the pulse width of the driving voltage, while in a second temperature region different from the first temperature region, the driving voltage is set to another constant value and the pulse width of the driving voltage is changed. It is characterized by the following.

Further, the present invention is characterized in that control is performed such that the drive voltage in the temperature region on the low temperature side is higher than the drive voltage in the temperature region on the high temperature side.

Further, the present invention is characterized in that the pulse width of the drive signal is shortened in response to a rise in temperature.

Further, the present invention is characterized in that both the driving voltage and the pulse width are changed at the boundary of the temperature region.

Further, according to the present invention, based on temperature information from the temperature detecting means for detecting the temperature of the liquid crystal element by the control means, any one of a plurality of temperature areas in which the temperature of the liquid crystal element has a predetermined temperature range. And controlling the driving voltage generating means for generating a driving voltage for driving the liquid crystal sandwiched between the pair of substrates so that the driving voltage in the temperature region to which the temperature belongs differs from the other temperature regions. , And the temperature of the liquid crystal element is compensated.
Further, the control means controls the drive signal generation means for generating a drive signal of a magnitude corresponding to the drive voltage, and changes the pulse width of the drive signal in accordance with the temperature within the temperature range so as to change the temperature of the liquid crystal element. Make compensation.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of a liquid crystal device according to an embodiment of the present invention. In FIG. 1, reference numeral 101 denotes a liquid crystal panel as a liquid crystal element, and 102 denotes a thermistor for detecting the temperature of the liquid crystal panel 101. After the temperature information from the thermistor 102 is input to a temperature detection circuit 108 constituting a temperature detection means together with the thermistor 102, the temperature detection circuit 108 outputs the panel control circuit 1 as temperature data.
05.

In the present embodiment, the thermistor 102 externally attached to the liquid crystal panel 101 has been described as the temperature detecting means. , The temperature of the liquid crystal panel 101 may be detected.

On the other hand, reference numeral 106 denotes a display data generator.
The data transmitted from the display data generator 106 is input to the panel control circuit 105, and is converted into scan address data and display data, respectively.

The panel control unit 10 as a control means
Reference numeral 5 denotes a scan electrode drive control signal to the scan electrode drive circuit 103a, which is a drive signal generation means, according to the scan address data and the temperature data from the temperature detection circuit 108, and a drive signal generation signal according to the display data and the temperature data. While the information electrode drive control signal and the image signal are respectively input to the information electrode drive circuit 103b as the means, the drive voltage control signal is input to the drive voltage generation circuit 104 as the drive voltage generation means according to the temperature data. ing.

Here, the driving voltage generating circuit 104
A predetermined scanning signal driving voltage and a predetermined information signal driving voltage are generated based on the driving voltage control signal from the panel control circuit 105, and are supplied to the scanning electrode driving circuit 103a and the information electrode driving circuit 103b, respectively. The scanning electrode driving circuit 103a and the information electrode driving circuit 103b
A scanning signal and an information signal are generated based on each driving voltage from the driving voltage generating circuit 104 and each control signal and image signal from the panel control circuit 105, and the liquid crystal panel 101 is driven at a predetermined driving frequency and driving voltage. It is supposed to.

The liquid crystal panel 101 is similar to that shown in FIG.
As shown in FIG. 1, a scanning signal electrode 201 and an information signal electrode 202 are formed in a matrix on a glass substrate, and the intersection of the scanning signal electrode 201 and the information signal electrode 202 constitutes one pixel 203. In the present embodiment, the display area of the liquid crystal panel 101 is 15 inches diagonally and the number of pixels is 12
80 × 1024.

The liquid crystal panel 101 has a pair of glass substrates 302, as shown in FIG.
And a liquid crystal cell 300 having a scanning signal electrode 201 and an information signal electrode 202 formed on the pair of glass substrates 302, respectively, and an alignment film 306 rubbed in parallel and in the same direction, and on both sides of the liquid crystal cell 300. Are provided with two polarizing plates (analyzer and polarizer) 301 and 305, respectively, and a liquid crystal 303 sealed between glass substrates. The transmission axes of the two polarizing plates 301 and 305 are in a crossed Nicols relationship, and the cell thickness of the liquid crystal cell 300 is about 1 μm.

Here, between the glass substrates of the liquid crystal cell 300, a ferroelectric liquid crystal (FLC / chevron) having the following physical properties is sealed as a first example of the present embodiment.

[0026] Spontaneous polarization Ps = 6 nC / cm ² (30 ° C.) Tilt angle Θ = 15 deg (30 ° C.) Dielectric anisotropy Δε = −0.2 (30 ° C.) A drive waveform as shown in FIG. 4 is applied to the information signal electrode 202. In addition,
In the figure, S1 to S3 represent a scanning signal, I represents an information signal, and "B" and "W" are each a selection period (1H).
The information signal is output from the information electrode drive circuit 103b based on the “black” and “white” image information.

(S2-I) and (S3-I) are each erased to "black" in the first half of the scanning signal, and then changed to "black".
, And a composite waveform applied to each pixel corresponding to the writing of “white”. here,
The voltage (V2 + V) applied to the pixel when writing “white”
3) is defined as a drive voltage Vop.

Further, in FIG. 2, the voltages V1 to V5 are supplied from the drive voltage generation circuit 104 of FIG. 1, and the panel control circuit 105 inputs the voltages to the drive voltage generation circuit 104 based on the temperature data. It changes according to the drive voltage control signal.

FIG. 5 shows the temperature T in this embodiment.
The change of the drive voltage Vop with respect to emp and the selection period 1H are shown. Here, the panel control unit 105 controls the liquid crystal panel 1 detected by the thermistor 102 when driving the liquid crystal.
Whether the temperature 01 belongs to a first temperature range having a predetermined temperature range (for example, 0 to 30 ° C.) or a second temperature range having a predetermined temperature range (for example, 30 ° C. or more) shown in FIG. It is determined that the driving voltage is fixed at 20 V when the pixel belongs to the first temperature range, and is always 15 V when the pixel belongs to the second temperature range.
And so on. By making the drive voltage in the lower temperature region higher than the drive voltage in the higher temperature region, the temperature of the liquid crystal panel 101 can be compensated.

The selection period (1H in FIG. 4) is the same as that in FIG.
For example, as shown in FIG.
The control is performed such that the pulse width decreases (shortens the pulse width) according to the temperature rise, for example, about 60 μs to about 60 μs in the second temperature region.

By thus shortening the pulse width of the drive signal corresponding to the temperature in each temperature region in accordance with the temperature rise, the temperature of the liquid crystal panel 101 can be compensated. . Note that the rate of change in the drive frequency in each temperature region may be the same or different. At the boundary of the temperature region, the drive voltage and the pulse width are both changed.

By the way, the control of the drive voltage and the selection period with respect to the temperature is performed based on the temperature data inputted to the panel control circuit 105, by controlling the scan electrode control signal, the information electrode control signal and the drive voltage control signal at predetermined timings. This is achieved by controlling the value.

That is, the selection period 1H is controlled by changing the frequency of a basic clock for generating a liquid crystal driving waveform to be supplied to the scanning electrode driving circuit 103a and the information electrode driving circuit 103b. This is performed by switching the reference voltage supplied to the voltage generation circuit 104.

By driving in this manner,
Good images could be displayed on the entire liquid crystal panel 101 over the operating temperature range of 0 ° C. to 50 ° C.

In the above description, the case where the liquid crystal is driven is divided into two temperature regions. However, the present invention is not limited to this, and the control described above is divided into three or more temperature regions. Is performed, a better image can be displayed.

Next, a second example of this embodiment will be described.

In this embodiment, the liquid crystal panel in the first embodiment is changed as follows. That is, the arrangement of the electrodes and the polarizing plate is the same as that of the first embodiment, except that a polyimide film (about 10 nm thick) is formed on one of the pair of glass substrates 302 of the liquid crystal cell 300, and the surface thereof is made of nylon. Rubbing treatment was performed in one direction using a cloth made of aluminum. The other substrate was subjected to a vertical alignment treatment by spin-coating a silane coupling agent (ODS-E). Further, after that, the two substrates were bonded together via silica beads having an average particle size of 2.0 μm, and bonded with a sealant.

A ferroelectric liquid crystal having the following physical properties was sealed in the gap. The liquid crystal has a so-called bookshelf structure in which the smectic layer does not have a chevron structure and has no bent portion in a non-spiral state sealed in a cell.

[0039] Spontaneous polarization Ps = 30 nC / cm ² (30 ° C.) Tilt angle Θ = 20 deg (30 ° C.) Dielectric anisotropy Δε = 0 (30 ° C.) In this embodiment, as shown in FIG. When the liquid crystal panel 101 was driven in accordance with the above method, for example, a good image could be displayed over the entire liquid crystal panel 101 under the following conditions.

[0040]

[Table 1] Next, a third example of the present embodiment will be described.

In this embodiment, a liquid crystal having an antiferroelectric phase exhibiting the following physical properties was injected into a liquid crystal cell substantially similar to that of the first embodiment (S ^* _CA is an antiferroelectric phase). However, the number of pixels is 6
40480, 1/240 duty (screen divided into two), cell thickness is about 2 μm, and the polarizing axis of one polarizing plate substantially matches the average molecular axis in the antiferroelectric state.

[0042] Spontaneous polarization Ps = 80 nC / cm ² (25 ° C.) Tilt angle Θ = 27.1 deg (25 ° C.) By the way, FIG. 6 shows a driving waveform when an antiferroelectric liquid crystal is used, and a scanning signal S1 is shown. , S2 include an erasing section, a selecting section, and a non-selecting section as shown in the figure, and an offset voltage is applied to the non-selecting section. Further, the polarity of the scanning signal can be inverted for each frame. In addition,
Vop indicates a voltage applied during the selection period of S1-I in FIG.

Then, similarly to the first embodiment, when driven according to the method shown in FIG. 5, for example, a good image could be displayed on the entire liquid crystal panel 101 under the following conditions. (ΔT is the width of the selection pulse; described in FIG. 6)

[0044]

[Table 2] Next, a fourth example of the present embodiment will be described.

In this embodiment, the liquid crystal panel in the first embodiment is changed as follows, and a twisted nematic mode having bistability is used. The principle content of this mode is described in JP-B-1-51818, and the driving method is described in detail in JP-A-6-230751.

Nematic liquid crystal composition (KN: manufactured by Chisso Corporation)
-4000) to an optically active agent (manufactured by Merck: S-811).
Was added to obtain a chiral nematic liquid crystal having a helical pitch P of 3.4 μm.

The cell was formed by forming ITO on two glass substrates, further forming a polyimide alignment film, and then performing a rubbing treatment. Each glass substrate is interposed via spacer beads.
The cells were bonded so that the rubbing direction was antiparallel, and a cell having a cell thickness d = 2.0 μm was prepared. The liquid crystal composition was injected into the liquid crystal cell, and two polarizing plates were further arranged on both sides of the cell to obtain a liquid crystal element. At this time, the pre-tilt angle was α = 4 °, and the initial orientation was π twist orientation.

The driving waveform shown in FIG. 7 was applied to this device under the following conditions.

Reset voltage (scanning signal: V1 = ± 30)
V, selection voltage (information signal: V2) = ± 1.5 to 2 V, 1/10 under driving conditions of reset pulse width (T1) = 2 ms
When 0 duty refresh scan was performed, 0 twist uniform orientation was formed, and "bright" was displayed.

When driven under the same conditions except that the selection voltage was set to 0 V, a 2π twist orientation was formed.
The display was "dark", and the contrast at this time was about 50.

Although FIG. 7 shows that the times T1 and T2 are almost the same, T1 is actually much longer than T2. In order to make the whole flow easier to understand, this is intentionally described.

As in the first embodiment, when driven according to the method shown in FIG. 5, a good image could be displayed on the entire liquid crystal panel 101 under the following conditions, for example.

[0053]

[Table 3]

[0054]

As described above, according to the present invention, the temperature of the liquid crystal element is compensated by setting the drive voltage in the temperature area to which the temperature of the liquid crystal element belongs to a predetermined constant voltage different from the other temperature areas. By doing so, sufficient temperature compensation of the liquid crystal element can be performed with a simple structure. Further, by changing the pulse width of the drive signal in accordance with the temperature of the liquid crystal element within the temperature range to perform the temperature compensation of the liquid crystal element, sufficient temperature compensation of the liquid crystal element can be performed with a simple structure. .

As a result, in a variety of liquid crystal display modes, a normal image can be displayed over a wide temperature range with a simple drive control circuit, and the liquid crystal device is inexpensive and has excellent display characteristics. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view of a liquid crystal device according to the present invention.

FIG. 2 is a plan view of a liquid crystal panel of the liquid crystal device.

FIG. 3 is a cross-sectional view of the liquid crystal panel.

FIG. 4 is a diagram showing an example of a driving waveform applied to a ferroelectric liquid crystal of the liquid crystal panel.

FIG. 5 is a diagram showing an example of temperature versus drive voltage control and temperature versus scan pulse width control.

FIG. 6 is a diagram showing an example of a driving waveform applied to an antiferroelectric liquid crystal of the liquid crystal panel.

FIG. 7 is a diagram showing an example of a driving waveform applied to a chiral nematic liquid crystal of the liquid crystal panel.

[Explanation of symbols]

 Reference Signs List 101 liquid crystal panel 102 thermistor 103a scan electrode drive circuit 103b information electrode drive circuit 104 drive voltage generation circuit 105 panel control circuit 108 temperature detection circuit 201 scan signal electrode 202 information signal electrode 302 glass substrate 303 liquid crystal

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-6-175108 (JP, A) JP-A-63-44636 (JP, A) JP-A-7-175041 (JP, A) JP-A-2- 179609 (JP, A) JP-A-2-96117 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/133 560 G02F 1/133 580 G09G 3/36

Claims (10)

(57) [Claims] 1. A liquid crystal device comprising a liquid crystal element configured to drive a liquid crystal sandwiched between a pair of substrates by applying a driving signal to electrodes formed on the pair of substrates. Drive voltage generation means for generating a drive voltage to be driven; drive signal generation means for generating a drive signal having a magnitude corresponding to the drive voltage; temperature detection means for detecting the temperature of the liquid crystal element; and the temperature detection means While determining which of the plurality of temperature ranges the temperature of the liquid crystal element belongs to based on the temperature information from the plurality of temperature ranges, the drive voltage of the temperature range to which the temperature belongs is determined by the other temperature range. The drive signal generation means controls the drive voltage generation means to have a predetermined constant voltage different from the drive signal generation means, and changes the pulse width of the drive signal according to the temperature within the temperature range. A liquid crystal device characterized by comprising a control means for controlling, the. 2. The control unit according to claim 1, wherein the control unit controls the drive voltage generation unit such that a drive voltage in the temperature region on the low temperature side is higher than a drive voltage in the temperature region on the high temperature side. The liquid crystal device according to the above. 3. The liquid crystal device according to claim 1, wherein said control means shortens a pulse width of said drive signal in response to a rise in temperature. 4. The liquid crystal device according to claim 1, wherein the liquid crystal is a liquid crystal having a memory property. 5. The liquid crystal device according to claim 4, wherein the liquid crystal is a ferroelectric liquid crystal or an antiferroelectric liquid crystal. 6. The liquid crystal device according to claim 4, wherein said liquid crystal is a bistable nematic liquid crystal. 7. A method for driving a liquid crystal device including a liquid crystal element configured to drive a liquid crystal sandwiched between a pair of substrates by applying a driving signal to an electrode formed on at least one substrate. When the temperature of the liquid crystal element is within a first temperature range having a predetermined temperature range based on temperature information from temperature detecting means for detecting the temperature of the liquid crystal element, the driving voltage is kept constant and While the pulse width of the voltage is changed, when in a second temperature region different from the first temperature region, the drive voltage is set to another constant value and the pulse width of the drive voltage is changed. Method for driving a liquid crystal device. 8. The driving method of a liquid crystal device according to claim 7, wherein the driving voltage in the temperature region on the low temperature side is controlled to be higher than the driving voltage in the temperature region on the high temperature side. 9. The driving method of a liquid crystal device according to claim 7, wherein a pulse width of the driving signal is shortened in accordance with a temperature rise. 10. The method according to claim 7, wherein both the driving voltage and the pulse width are changed at the boundary of the temperature region.